1. Field of the Invention
This invention relates to an electric vehicle control device, and in particular relates to a control device for an AC/DC electric vehicle which is to be driven straight through a zone in which the power obtained from the overhead wire is AC and a zone in which it is DC.
2. Description of the Related Art
FIG. 5 shows the construction of a conventionally known electric vehicle control device for controlling an AC/DC electric vehicle. This prior art electric vehicle control device is equipped with: a collector 1 that collects power from the overhead wire (not shown), a first circuit breaker 2 for power circuit breaking, a changeover device 3 for changing over AC and DC, a transformer 4 that transforms AC power, a grounding brush 5 that grounds the AC primary current, a rectifier 6 for rectifying the AC obtained on the secondary output side of transformer 4, a smoothing inductor 7 connected to the output side of this rectifier 6, and an AC/DC converter 8 for changing over AC and DC and whose operation is linked to that of changeover device 3. There are further provided a second circuit breaker 9 arranged on the output side of AC/DC converter 8, and an electric motor control circuit 11 that drives and controls electric motor 10, whose power source is the DC power obtained on the output side of this second circuit breaker 9. Additionally, an auxiliary power source device 12 is connected in parallel with the input side of electric motor control circuit 11. Furthermore, in order to detect ground faults of the circuit in the AC power zone, there is provided a ground relay 13 between the secondary side of transformer 4 and ground. A voltage relay in employed for this relay 13.
In this prior art electric vehicle control device, in the AC power zone, AC/DC changeover device 3 and AC/DC converter 8 are arranged on the AC side a, so that AC power obtained through collector 1 and circuit breaker 2 is stepped down by transformer 4, rectified by rectifier 6 and smoothed by smoothing inductor 7. The smoothed power is then supplied to electric motor control circuit 11 through second circuit breaker 9, and also supplied to auxiliary power source device 12 without passing through the second circuit breaker 9.
In DC power source zones, AC/DC changeover device 3 and AC/DC converter 8 are changed over to the DC side d, so that DC power obtained through current collector 1 and circuit breaker 2 is supplied to electric motor control circuit 11 through second circuit breaker 9 and is also directly supplied to auxiliary power source device 12 without passing through second circuit breaker 9. Moreover, in such DC power source zones, transformer 4 is isolated from current-carrying locations by means of AC/DC changeover device 3 and AC/DC converter 8, so as to avoid DC power flowing into transformer 4 from the overhead wire.
Problems in such a prior art electric vehicle control device were that two changeover mechanisms were required for the AC/DC changeover device 3 and AC/DC converter 8 in order to effect changeover of AC and DC. This inevitably increased the size of the equipment constituting the electric vehicle control device and also made maintenance thereof burdensome.
In recent years, pulse width modulating converters are being employed using GTO thyristors instead of a rectification circuit using diodes, inverter devices are used for the electric motor control circuit, while an induction motor is employed as the electric motor, and also a static converter is used as auxiliary power source device. Selection of the most appropriate AC/DC changeover circuit is an important challenge in applying these devices to an AC/DC electric vehicle control device.